The prior art discloses magnetoresistive (MR) reproducing heads that operate based on the magnetoresistive effect exhibited by thin films composed of certain materials. A read head incorporating an MR transducer detects magnetic field signals through the resistance changes of an MR transducer element as a function of the amount and direction of the magnetic flux being sensed by the MR transducer element.
Responsive to the drive toward increased recording density, batch fabrication processes have been developed for efficient, high volume production of miniaturized MR transducers. Typically, a batch fabrication process for MR transducers employs known thin film manufacturing techniques to produce a plurality of such transducers on a wafer in "wafer level" processing. A wafer is then sliced row-wise into a 1.times.n array of transducers which are polished in "row-level" processing and then individuated by cutting rows into separate sliders. Each slider includes a head structure with an MR reproducing head.
It is known to selectively vary construction details and manufacturing parameters in order to yield an MR transducer having a particular magnetic state which optimizes transducer operation. In this regard, an MR transducer may comprise soft or hard biasing elements and may be produced by a batch process in which magnetic fields are applied at certain steps during wafer level processing. These components set magnetic characteristics of the thin film MR layer ("the MR stripe") such as magnetization direction, field orientation, and so on. See, for example, C. D. Mee et al, "MAGNETIC RECORDING, Vol. I", McGraw-Hill, New York, 1987, pp. 270-302.
The magnetic characteristics of the MR stripe are initialized by the application of a magnetic field to the MR head. Currently, the initialization step takes place at the wafer level and at the row level, depending upon the circumstances and requirements of manufacturing and assembly.
However, some processing operations that occur during and after row-level processing have been proved to alter the magnetic state of MR transducers. In this regard, the inventors have concluded that intentional and accidental insults to an MR transducer occurring during and after row level processing can cause the formation of domains in the thin film magnetoresistive material layer, alter the magnetic orientation of exchange layers in soft bias transducers, and disorient and demagnetize magnetized layers in hard bias transducers. Singly and collectively, these effects can alter the magnetic state of an MR transducer. The inventors have found that alteration of the magnetic state can significantly degrade the quality of MR transducer operation. Relatedly, MR transducers that exhibit high amplitude response during row-level testing can fall into low amplitude response after they are sliced from rows and mounted on media drive assemblies.
The prior art does not disclose a process for manufacturing media drives in which the magnetic state initially established for MR reproducing heads during wafer level processing is reinitialized during media drive assembly steps.